用NPOI从DataBase到Excel

NPOI的C# Helper代码

        public static void WriteExcel(DataTable dt, string filePath)
        {
            if (!string.IsNullOrEmpty(filePath) && dt.Rows.Count > 0)
            {
                HSSFWorkbook wk = new HSSFWorkbook();
                ISheet sheet = wk.CreateSheet(dt.TableName);

                //列头
                IRow headerRow = sheet.CreateRow(0);
                for (int i = 0; i < dt.Columns.Count; i++)
                {
                    headerRow.CreateCell(i).SetCellValue(dt.Columns[i].ColumnName);
                }

                //填充内容
                for (int i = 0; i < dt.Rows.Count; i++) //注意条件dt.Rows.Count
                {
                    IRow row = sheet.CreateRow(i+1);
                    for (int j = 0; j < dt.Columns.Count; j++)//注意条件dt.Columns.Count
                    {
                        row.CreateCell(j).SetCellValue(Convert.ToString(dt.Rows[i][j])); //注意这里写法
                    }
                }
                //写入到客户端
                using (MemoryStream ms = new MemoryStream())
                {
                    wk.Write(ms);
                    using (FileStream file = new FileStream(filePath, FileMode.Create, FileAccess.Write))
                    {
                        byte[] data = ms.ToArray();
                        file.Write(data,0,data.Length);
                        file.Flush();
                    }
                    wk = null;
                }

            }
        }